Efficient Olefins Epoxidation on Ultrafine H2O-WOx Nanoparticles with Spectroscopic Evidence of Intermediate Species

Design and synthesis of high-performance heterogeneous catalysts are of great interests in chemical industries. Herein, we combined space-confinement pyrolysis with post-modification oxidation strategy to construct ultrafine H2O coordinated WOX nanoparticles (average diameter 2.24 nm) embedded into porous carbon matrix. With the unique H2O coordinated environment, the catalyst exhibits high activities in olefin epoxidations using H2O2 as oxidant. In epoxidation of cis-cyclooctene tests, the turnover frequency (TOF) of the catalyst can reach as high as 949 h-1, an activity comparable to the highest of all reported early transition-metal (TM) based catalysts. UV-Vis spectra and controlled catalytic experiments are employed to ascertain the possible active site in the catalyst: compared with traditional WO3 and peroxide coordinated W-(η2-O2) species, the water coordinated H2O-WOX can transform into hydroperoxide HOO-WOx in the presence of H2O2, and the HOO-WOx species can be further activated by proton acid ...